Magnetically Driven Precession of Warped Disks and Millihertz Variabilities in Accreting X‐Ray Pulsars

Shirakawa, Akiko; Lai, Dong

doi:10.1086/324548

Cited by 39 publications

(59 citation statements)

References 45 publications

(43 reference statements)

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“…This is similar to the Lense-Thirring precession [2]. This can explain the mHz QPOs for strongly magnetized neutron stars [3]. The effect of nonlinear coupling between g-mode oscillations in a thin relativistic disk and warp has also been examined [4] for a static compact object.…”

Section: Introductionsupporting

confidence: 62%

Predicting spin of compact objects from their QPOs: A global QPO model

Mukhopadhyay¹

2008

AIP Conference Proceedings

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Abstract.We establish a unified model to explain Quasi-Periodic-Oscillation (QPO) observed from black hole and neutron star systems globally. This is based on the accreting systems thought to be damped harmonic oscillators with higher order nonlinearity. The model explains multiple properties parallelly independent of the nature of the compact object. It describes QPOs successfully for several compact sources. Based on it, we predict the spin frequency of the neutron star Sco X-1 and the specific angular momentum of black holes GRO J1655-40, GRS 1915+105.

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Section: Introductionsupporting

confidence: 62%

Predicting spin of compact objects from their QPOs: A global QPO model

Mukhopadhyay¹

2008

AIP Conference Proceedings

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“…A number of other X-ray pulsars have shown flares at intervals comparable to those in the optical light curve of the second night which produce mHz QPO features in the PDS: Her X-1 (Boroson et al 2000), LMC X-4 (Moon and Eikenberry 2001) and 4U 0115+63 (Soong and Swank 1989). A magnetically driven warping/precessing model was used to explain mHz variability in the X-rays and UV/optical for these sources (Shirakawa and Lai 2002). A 1 mHz optical QPO, without a counterpart X-ray QPO at that frequency, was discovered in 2001 (Chakrabarty et al 2001) for 4U 1626-67.…”

Section: Discussionmentioning

confidence: 99%

SALT observation of X-ray pulse reprocessing in 4U 1626−67

Raman¹,

Paul²,

Bhattacharya³

et al. 2016

Mon. Not. R. Astron. Soc.

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We investigate optical reprocessing of X-rays in the LMXB pulsar 4U 1626-67 in its current spin-up phase using observations with Southern African Large Telescope (SALT), nearsimultaneous observations with Swift-XRT and non-simultaneous RXTE-PCA observations and present the results of timing analysis. Using SALT observations carried out on 2014, March 5 and 6, we detect some interesting reprocessing signatures. We detect a weak optical Quasi Periodic Oscillation (QPO) in the power density spectrum on March 5 at 48 mHz with a fractional rms of 3.3% in spite of the fact that source shows no corresponding X-ray QPO in the spin-up phase. In the light curve obtained on March 5, we detect a coherent pulsation at the spin period of ∼7.677 s. A previously known, slightly down-shifted side-band is also detected at 129.92 mHz. The frequency spacing between main pulse and this side-band is different from earlier observations, though the statistical significance of the difference is limited. The light curve of March 6 displays short time-scale variability in the form of flares on time-scales of a few minutes. Folded pulse profiles resulting from data of this night show an interesting trend of pulse peak drifting. This drift could be due to i) rapid changes in the reprocessing agent, like orbital motion of an accretion disc warp around the neutron star or ii) intrinsic pulse phase changes in X-rays. We also examine some X-ray light curves obtained with RXTE-PCA during 2008-2010 for pulse shape changes in short time-scales during X-ray flares.

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“…Periodic or semi-periodic long term intensity variations are known to be present in a few systems like Her X-1, LMC X-4 and SMC X-1 (Clarkson et al 2003b;Boyd et al 2004) which may have a different origin compared to the long term intensity variations in other low and high mass X-ray binaries (Paul et al 2000;Clarkson et al 2003b;Still & Boyd 2004). The quasi-periodic long term intensity variations observed in many X-ray binaries can be due to the precession of a warped inner accretion disk (Shirakawa & Lai 2002). A stable superorbital period of the warped disk is more common in the high magnetic field neutron star systems (Oglivie & Dubus 2001).…”

Section: Introductionmentioning

confidence: 99%

Accretion mode changes in Centaurus X-3

Paul¹,

Raichur

Mukherjee³

2005

A&A

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We report here discovery of the existence of two different accretion modes in the high mass X-ray binary pulsar Cen X-3 during its high states. The multiband X-ray light curves of Cen X-3 lasting for more than 3400 days obtained with the All Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE) shows many episodes of high and low X-ray intensities. The high intensity phases last between a few to upto 110 days and the separation between two high intensity phases also varies widely. One remarkable feature deduced from the RXTE-ASM light curves is that during these high intensity phases, Cen X-3 manifests in two very distinct spectral states. When the source makes a transition from the low intensity phase to the high intensity phase, it adopts one of these two spectral states and during the entire high intensity phase remains in that particular spectral state. During December 2000 to April 2004, all the high intensity episodes showed a hardness ratio which is significantly larger than the same during all the high states prior to and subsequent to this period. It is also found that most of the soft outbursts reach a nearly constant peak flux in the 5-12 keV band. For comparison, similar analysis was carried out on the long term X-ray light curves of three other X-ray binary pulsars Her X-1, Vela X-1, and SMC X-1. Results obtained with these sources are also presented here and we found that none of the other sources show such a behaviour. From these observations, we suggest that Cen X-3 has two different accretion modes and in the course of nine years it has exhibited two switch overs between these.

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Magnetically Driven Precession of Warped Disks and Millihertz Variabilities in Accreting X‐Ray Pulsars

Cited by 39 publications

References 45 publications

Predicting spin of compact objects from their QPOs: A global QPO model

Predicting spin of compact objects from their QPOs: A global QPO model

SALT observation of X-ray pulse reprocessing in 4U 1626−67

Accretion mode changes in Centaurus X-3

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